The present invention relates generally to methods for processing substrates, and the resultant substrates, by employing radiation pulses, and more particularly to such methods that allow introducing a dopant into a surface layer of the substrates.
A variety of techniques are utilized for doping semiconductor substrates. For example, crystalline silicon can be doped to about 1% atomic concentration via irradiation of silicon wafers with a train of femtosecond radiation pulses in the presence of a dopant-containing compound. For example, a silicon wafer can be doped with sulfur to about 1% atomic concentration by irradiating the wafer with femtosecond radiation pulses while exposed to a sulfur donor, such as SF6. The resulting doped silicon can exhibit several highly desirable optoelectronic properties. For example, it can exhibit significant absorption of radiation wavelengths longer than about 1100 nm. In fact, such doped silicon can be utilized to fabricate silicon photodiodes that operate well into the infrared.
However, the known methods for producing such doping can also cause significant damage to the silicon wafers. For example, they can cause the formation of a quasiperiodic array of spikes and ridges on the silicon surface. Such surface structures can cause difficulties in utilizing the doped wafers in a variety of applications. For example, in case of photodetector fabrication, they can render the use of many traditional measurement and handling techniques, as well as manufacturing processes, difficult.
Accordingly, there is a need for improved methods for radiation processing of substrates, and particularly for improved methods of doping substrates. There is also a need for doped substrates exhibiting enhanced surface morphologies.